TNF and rheumatoid arthritis: In the SMART study, involving 208 patients with active RA in whom anti-TNF agents had failed or were contraindicated, serum IgG > 12.66 gm/liter (upper limit of normal) arose as independent predictors of response to rituximab with an OR of 2.11 and synergistic with RF and/or ACPA [120], confirming that anti-CD20 treatments may be particularly indicated in the B cell-driven subtype of RA.